[chupathingie]

I think your two-star alignment is dropping off due to lens distortion

That’s the heart of it, I’m thinking. I’ve been wanting something that can “de-pincushion” images for ages, so I can stack short exposures from a stationary camera. So far I’ve had no luck and have not revisited the idea in some years.

[chupathingie]

I can see the sense in doing darks before/during/after. Getting clean images of low-light targets is time consuming with a DSLR. It’s a good thing that celestial objects don’t move much.

I’ll second the 3 reasons for winter shooting. The skies in the Adirondacks were amazing in winter. Too friggin cold to sit by the scope for hours, tho. Below 0F was common enough. Brrrr.

[chupathingie]

I think the author of that article is lacking… 32 is definitely not overkill. Those diminishing returns offer a significant increase in the amount of detail you can tease out of an image.With only 9 subs, you can’t stretch levels very far. You don’t start getting a smooth, somewhat noise-free background until you hit 20+ subs. Seriously, the more the better. More data= cleaner images.

This guy knows what he’s talking about… lots of good info for those wanting to get to grips with what it takes to get good data for images:
http://www.saratogaskies.com/articles/cookbook/index.html

Also, if you’re going to stack, take the time to shoot off 1/2 dozen darks with the lens cap on of the same duration and (important!) at the same temperature. I shoot darks in the middle of my shoots. These can be averaged and used to reduce noise and hot pixels before you start to stack.

This was done without darks, shot as JPEG (this was my 1st attempt, I barely had a clue). In other words, done wrong from a noise reduction standpoint. 36 exposures and shot from the middle of Dallas/Fort Worth. Horrible light pollution.30 second exposures. I should have shot in RAW (duh!) and taken the time for darks. A dozen well-collected subs will just start to get you to where you can stretch the contrast to the point of making the wispy details come out without making all that noise come out as below.

Have a look here:
http://ap.x-wing.ca/gallery/v/Nebulae/NGC7635_67x600s_PI_A1_A1.jpg.html?g2_imageViewsIndex=2
Look at the stats… 67 10-minute subs. Obviously done over multiple sessions (no, not one of mine…someday, maybe…).

[chupathingie]

yup. Or you can download one of the free automated tools built for the purpose, or purchase one of the commercial ones. Personally, I’ve had better luck with the manual stacking (as tedious as it is). I’ve not stacked anything in ages, tho… I really need a decent mount to extend my exposure times.

[chupathingie]

There are several ways to stack, but the simplest method is to is to stack multiple exposures on top of each other in layers. The bottom layer gets 100% opacity, second gets 50%, third gets 33%, 4th gets 25% etc. This gives a straight average of image data, which reinforces the actual data while minimizing noise. Stacking 30+ images knocks the noise floor *WAY* down, and allows you to aggressively stretch levels (always do this in 16bits/channel) to increase the contrast of the faint fuzzies in the sky. This even works with 8-bit channel images, stacking can give you a 16-bit image that can be stretched far more than if averaged into an 8-bit image. It’s not as good as starting with 16-bit RAW-to-tiff, but it’s an improvement over the base 8-bit.

[chupathingie]

Craven, if the halos are blue, that’s Chromatic Aberration (CA). The only things I know that can be done about that is shoot at a higher f-stop, use better glass ($$$), or correct via software in post. With regards to the first 2, even L-Series lenses don’t like astrophotography much wide open, although the fixed-focal length telephoto lenses seem to have much better CA characteristics.

[chupathingie]

If you’re feeling handy, google “barn-door mount”; a cheap home-brew alternative to an equatorial mount.
While you can get decent wide-field shots from a tripod, shooting the night sky with a 300mm will need some kind of tracking mount. You’ll get obvious streaks in a very short few seconds with a stationary camera.

In-camera noise reduction is fine unless you’re planning on taking many long exposures. So if you do make a barn-door, turn the in-camera noise reduction off. Instead, run off a dozen shots in the middle of your shoot at the same settings as your exposures with the lens cap on. Average these together and subtract from each of your exposures before you do any other processing. This will really knock a lot of noise out.

If there’s a moon, or nearby light source lighting up the sky, take a shot at full in-focus. Process like the others for noise, then subtract this blurred image from your shot to remove (or reduce) the gradient from the offending light source. I used this trick a lot when I was shooting from within the DFW metroplex area to knock out the horrible light pollution. You can also blur the image you want to process and use that to subtract, just make sure it’s *really* blurred or you’ll kill any nebulae and the milky way in the final.

Shoot wide-open and look for any blue halos around your stars and also for any non-round stars on the edge of the field. If you see either, close down by a stop and try again. There’s a trade-off between image quality and brightness.

Things you can capture with a 300mm: In addition to the Andromeda Galaxy (which fills nearly the entire field of view at 300mm) and the Orion nebula mentioned above, I’ve taken images of M16, the Trifid nebula, the Hercules Cluster… I even managed one image of the Ring nebula. Most of the Messier Catalog objects can be managed with a DSLR if you can track.

I need to work a lot more OT to get that Losmandy G11…. *sigh*

[chupathingie]

ooooohhhh… this got the gears spinning for me… then I found out (like most neat ideas) that someone had already done what popped into my head…
http://www.galerie-photo.com/roto-pinhole.html
Still looks like a fun project, if a bit involved…

[chupathingie]

I have a nikon one, 24-70/2.8. It was kind of disappointing in person, though.

Dang, that’s too bad… I’d be all over one that looks as good IRL.

[chupathingie]

I think I can get by starting with just a new proc and RAM (I have a motherboard…) =P

That was my original plan, but with the wife’s PC going out, she gets all the innards from my current rig. At least this way I wound up with an upgrade to DDR3 and at twice the freq as well.

Someday I’ll be calling Astronomics for some hardware, but not if I have to keep updating the home PC front…

[chupathingie]

I’ve got 4G in my current rig, but then I caught the “hi-rez images” bug. What a slap-down that was. Multiple 120meg tiffs being fed into the works made very short work of it. This build would have only cost me $500 but for the RAM. $114 per 4G stick, so 4 of those added up in a hurry. Makes me glad Newegg didn’t have any boards capable of 32G… the Mad Scientist in me was seriously considering it.

Even tho OT seems a continuous option where I work (all ya gotta do is answer the home phone when it rings…something breaks every day), I seriously need some time off. There are so many weekend road trips to some amazing SW scenic spots that I want to do mad-crazy 500MP images of.

[chupathingie]

well except money 🙂

That’s the painful truth of it. I’ve been working like a plowhorse for the past few months and throwing all my O.T. at getting debts killed off. Breaking out the credit card for this was uncomfortable to say the least. If I’m lucky, this rig will keep me satisfied for the same 3 years the last one did.

[chupathingie]

hahahhaah… apparently the theiving wretch has taken his site down. Personally I think anyone who does this needs to have their name prominently in the spotlight long enough to effectively ruin any chance of them making a living in the field. Let ’em flip burgers and contemplate where they went wrong.

[chupathingie]

Hah. Nice to see the crowd catching a clown in a scam.

[chupathingie]

Would anyone notice if I drooled on the floor in here?

Just what I need…something ELSE to want to spend money on.

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